External Intercostal Muscle Under the Skin, Posterior View

Description

Posterior thoracic wall anatomy is presented with the skin reflected to expose the rib cage and the external intercostal muscles occupying the intercostal spaces near the rib angles. Oblique external intercostal fibers run infero-anteriorly from the inferior border of each rib to the superior border of the rib below, sitting superficial to the internal intercostals and deep to the more superficial back musculature. The spinous processes form a midline landmark, while the ribs sweep laterally from the thoracic vertebrae to frame the interspaces. Color separation distinguishes skeletal elements from muscle layers. Attention to the posterior extent of the external intercostals matters because these fibers are thickest near the costal angles and transition anteriorly into the external intercostal membrane, a point that often confuses learners when they compare cadaveric dissection with imaging or surface anatomy. Palpation and procedures cluster here: posterior intercostal spaces are where you teach intercostal neurovascular bundle location (in the costal groove along the inferior rib margin) and where posterior rib fractures can compromise ventilation by limiting rib elevation during inspiration. Clear fiber direction also supports explanation of the bucket-handle component of rib motion during respiration. Use this artwork in gross anatomy and respiratory mechanics teaching to anchor the concept of intercostal layering, fiber orientation, and their relationship to rib landmarks at the back. It also fits surgical education content on thoracostomy and intercostal nerve block planning by reinforcing where the interspace lies relative to the rib and vertebral column in a male posterior view. Anatomical accuracy verified by SciePro's Medical Advisory Board.